There is also the famous Bruton Music library which divided their catalog by genre. The disc sleeves are color-coded to match each section of music. On the 1983 sample disc "Bloop", it's considered to be the Universal Galactic Standard for Coding.
BRA – Fanfares, Links, Bridges, Stings
BRB – Jingles (compiled from various Bruton albums)
BRC – Neutral, Solo Instruments, Sadness
BRD – Leisure, Pastoral, Nature, Tenderness, Romance
BRE – Children, Animation
BRF – Comedy, Parodies
BRG – Happy, Bright, Open Air, Sport
BRH – Contemporary, Pop, Rock
BRI – Futuristic, Electronic
BRJ – Theme Sets, Documentary & Drama Suites
BRK – Action, Pace, Danger, Force Of Elements
BRL – Industry
BRM – Suspense, Tension
BRN – Grandiose, Impressive, Panoramic
BRO – Historical, Period
BRP – Classical, Semi-Classical, Religious, Serious Vein
BRQ – Military, Marches
BRR – Folk, Nationalistic, Known Works
BRS – Jazz, Dance